1. Field of the Invention
The present invention relates to an image forming system, an image distribution apparatus, and an image forming method. In particular, the present invention relates to an image forming system comprised of a plurality of image forming apparatuses and an image distributing apparatus that distributes image data to the plurality of image forming apparatuses, an image distribution apparatus to which a plurality of image forming apparatuses are connected and which distributes image data to the plurality of image forming apparatuses, and an image forming method applied to the image forming system.
2. Description of the Related Art
Conventionally, to melt a developing agent (toner) in a thermally fixing process in xerography, a transfer sheet with toner adhered thereto is passed between fixing rollers which are controlled to have a high temperature of about 160 to 200° C. In the case where a normal transfer sheet is used, the transfer sheet itself shrinks slightly in the fixing process due to evaporation of moisture absorbed in the transfer sheet or for other reasons. The transfer sheet returns to its approximately original size if the temperature of the transfer sheet is lowered to the ambient temperature and the transfer sheet absorbs moisture in the air.
However, in double-sided printing in which the second side of a transfer sheet is printed immediately after the first side thereof is printed, an image is printed on the second side in a state in which the transfer sheet has been reduced in size immediately after toner is thermally fixed on the first side. For this reason, when the transfer sheet has returned to its original size, the size of an image printed on the second side is greater than that of the image just printed on the second side by an amount corresponding to the shrinkage amount of the transfer sheet. To solve this problem, an image forming apparatus has been proposed which detects the shrinkage amount of a transfer sheet immediately after fixing, and performs printing after reducing the size of an image to be printed on the second size according to the detection result, so that when the transfer sheet has returned to its original size, the size of an image printed on the second size can be equal to its original size, i.e., when the transfer sheet has returned to its original size in the case where images, which should originally be the same in size, are printed on the first side and second sides, the sizes of the printed images can be equal.
In a conventional large-sized printer system to which a wide variety of printers having different functions and capabilities are connected, the respective printers are caused to form desired images on transfer sheets, and the transfer sheets on which the images have been formed are bound up.
However, the plurality of printers constituting the above conventional printer system differ in amount of heat applied to a transfer sheet during fixing according to print methods such as full-color/black-and-white and print speed, and thus differ in shrinkage amount of a transfer sheet during fixing. Therefore, in double-sided printing, if images to be printed on the second sides by the respective printers are reduced by the same amount, the sizes of some images printed on the second sides may be different from the original sizes. It should be noted that some transfer sheets may not perfectly return to their original sizes even though the transfer sheets absorbs moisture in the air after fixing, and the degree to which a transfer sheet returns to its original size depends on the shrinkage amount of the transfer sheet during fixing. Therefore, in either double-sided printing or one-sided printing, images printed on respective transfer sheets by the plurality of printers may be different in size when enough time has elapsed after fixing although the images should originally be the same in size.
Under these circumstances, when transfer sheets printed by respective printers having different functions and capabilities are bound up, there is the problem that images printed on the transfer sheets are different in size although they should originally be the same in size.